Superregenerative magnetron receiver



March 31, 1942.

v R. A. BRADEN $277,841 SUPERREGENERATIVE MAGNETRON RECEIVER Original Filed Feb. 29, 1940 H MIKIEP 'MODULfiV/O/V FREQUENCY 4MP; fl/VD DETECTOR Rene A. Braden I omeg Patented Mar. 31, 1942 'SUPERREGENERATIVE MAGNETRON RECEIVER Rene .A. Braden, "Coilingswood, vN. -J., assignor to ,Radio Corporation 'of America, a corporation of Delaware Application February 29, 1940, Serial No. 321,550, which is *a division of application Serial No. "187,942, January 31, 1938,, .now Patent No.

2,211,091, :dated August 13, 1940.

Divided and this application January 24, 1941, Serial No.

6 Claims.

My invention relates to ultra short wave receivers, and more particularly to a receiver having a superregenerative magnetron detector.

This application is a division of my copending application Serial No. 321,550, filed February 29, 1940, for a Superregenerative magnetron receiver, which is in turn a division of my application Serial No. 187,942, filed January 31, 1938, which issued as United States Patent No. 2,211,091, on August 13, 1940.

The practice of superregeneration as applied to thermionic detectors operating in the usual range of radio signalling frequencies is well known. I have discovered that the conditions causing superregeneration which results in the increased sensitivity of an oscillating detector can be applied to a magnetron. Essentially these conditions are met by a detector which is capable of self-oscillation when suitable values of electrode potentials are applied and in which oscillations are interrupted by periodic variations of the electrode potentials.

It is an object of this invention to provide means for obtaining superregeneration in a magnetron. 1

My invention will be better understood from the following description when considered in connection with the accompanying drawing. Its scope is indicated by the appended claims. The figure of the drawing is the circuit diagram of a circuit for producing superregenerative action by means of a variable impedance connected across a transmission line in the oscillatory circuit.

Referring to the drawing, ultra short wave signals are received on the antenna I and fed by transmission line I5I, I53 to the anode electrodes 3 and 5 of the magnetron I61, which also includes a conventional linear cathode I energized by a battery 9, or the like. An electro or permanent magnet for producing a strong magnetic field which surrounds and is substantially parallel to the cathode is represented by the pole pieces 2 and I.

Anode potential for the magnetron is supplied by a battery 3| which is connected to the midpoint or electrical center of the antenna I 5, or an equivalent point, through a resistor i9 and a radio frequency choke H. A voltage corresponding to the modulation frequency component of the received signal is developed across resistor I9. This voltage is impressed on the output device, such as a modulation frequency amplifier and detector 29, through a coupling capacitor 21.

Quenching of the signal frequency oscillations is obtained by means of a damping tube I69 connected to a voltage loop in a transmission line I5I, I53 between an antenna l5 and a magnetron detector I6'I. This tube may be a magnetron or other thermionic tube. The transmission line is resonant at signal frequency. It is of suflicient length to provide the proper matching between antenna and oscillator and in addition to have available at least one voltage loop. Tube I69 is preferably connected to the transmission line at a voltage loop by very short leads. The anode electrodes I55 and I5! may be incorporated as a section of the transmission line instead of bein attached by separate leads. While the tube I69 may be operated as a negatively biased, positive plate triode, I prefer to operate it with a positive grid and a small positive or negative bias on the anodes.

Tube I69 consists of two anode electrodes I55 and I 51 which are respectively connected to lines I5I and I53. A cathode I59 is energized by a battery 9. An accelerating grid I6I which is between the cathode and the anodes is connected to one terminal of inductor I65. The remaining terminal is connected through a source of grid potential FM to one side of the cathode. The anodes are at a high positive potential with respect to ground. A battery I63 is connected between one side of the cathode and the high side of battery 3I. The polarity and'potential of battery I 63 may be adjusted to obtain the desired cathode-anode voltage.

The potential of accelerating grid I BI is varied by the quench frequency oscillations which are impressed on it from an oscillator 25. The effect of this is to vary the shunt impedance of the tube I69 across the transmission line. The short-circuiting effect which is produced in the magnetron I6I interrupts its signal frequency oscillations at the quench frequency, and superregeneration takes place.

While I have shown the damping tube I69 connected across the transmission line at a voltage loop, it would also be effective if coupled to this point by a resonant transmission line of suitable characteristics.

I claim as my invention:

1. In an ultra high frequency receiver consisting of an antenna, a magnetron oscillating at signal frequency, a transmission line connecting said antenna to said magnetron, said line being resonant at said signal frequency and having at least one voltage loop between said antenna and said magnetron, and means for indicating demodulated signals, the method of obtaining superregenerative detection which comprises varying the shunt impedance of said transmission line at said voltage loop at a quench frequency, thereby interrupting said signal frequency oscillations at the quench frequency.

2. In a superregenerative detector, the combination including an oscillating detector, a standing Wave oscillatory circuit connected to said detector, variable impedance means connected across said oscillatory circuit, and means for varying the impedance of said variable impedance means at an inaudible frequency to produce superregenerative detection by interrupting the oscillations of said detector.

3. A device of the character described in claim 2 in which said variable impedance means comprises a vacuum tube having a pair of anodes connected to said oscillatory circuit, a cathode, and a grid for varying the impedance of said variable impedance means.

4. A device of the character described in claim I and variable impedance means in shunt with said circuit for interrupting said oscillations at a su personic rate.

6. In a superregenerative detector, the combination including an oscillating magnetron detector, an antenna, a standing wave oscillatory circuit coupling said antenna to said detector, mean including a variable impedance electronic device connected across said line for interrupting the oscillation of said detector at a supersonic rate, and output means for deriving rectified currents from said detector.

RENE A. BRADEN. 

